The present invention relates to one member constituting a packaging material which is used for storage, transportation and mounting of electronic components and which can protect the electronic components from staining and, for mounting of the electronic components on a substrate for electronic circuit, enables alignment and taking-out of the electronic components; that is, a cover tape which can be sealed to a plastic-made carrier tape having pockets for storage of electronic components, formed therein.
Electronic components to be surface-mounted, such as IC, transistor, diode, capacitor, piezoelectric resistor and the like are supplied by being packed in a packaging material comprising (a) a plastic-made carrier tape in which pockets for storage of electronic components have been regularly formed by embossing, in a shape corresponding to those of the electronic components and (b) a cover tape which can be sealed to the carrier tape. The electronic components contained in the packaging material are automatically taken out from the packaging material after the cover tape has been peeled, and are surface-mounted on a substrate for electronic circuit. Electronic components have become smaller, lighter and thinner recently.
Meanwhile, the speed of surface mounting has increased and the speed at which the cover tape of the packaging material is peeled from the carrier tape, has increased as well. As a result, a pulsation phenomenon, that is, a phenomenon in which the strength when peeling is made (this strength is hereinafter referred to as peeling strength) fluctuates high and low, appears strikingly and jumping troubles caused by jumping-out of packed electronic components from the carrier tape are increasing.
When the electronic components packed in a packaging material are relatively large, the peeling strength of the packaging material is often set high beforehand in order to prevent the electronic components from jumping out from the carrier tape during transportation. In that case, however, if the peeling strength changes with time and becomes too high, the cover tape is difficult to peel smoothly during mounting, which invites, in some cases, a trouble of being incapable of taking out the electronic components or a trouble of cover tape rupture. The trouble associated with the peeling strength has been prevented by laminating an adhesive layer film obtained by using a mixture of several kinds of resins, onto a base layer film such as biaxially oriented polyester film or the like, by dry lamination or extrusion lamination.
The trouble appearing during mounting, such as cover tape rupture or the like has been prevented by laminating two oriented films with each other by dry lamination or the like to obtain a tough base layer.
In any of these countermeasures, however, the step of film formation and the step of lamination are independent, which requires a long-time process, incurs a high production cost, and does not satisfy the recent requirement of lower cost for electronic components.
The electronic components contained in a packaging material are automatically taken out after the cover tape of the packaging material has been peeled, and are surface-mounted on a substrate for electronic circuit. At that time, if the peeling strength of the cover tape has a large difference between the maximum value and the minimum value, there are caused cases that the carrier tape waves and the electronic components contained therein jump out; if the peeling strength is too high, there are caused cases that the cover tape cuts; and if the peeling strength is too small, there appears a case that the cover tape is peeled off before the mounting step is reached and the electronic components are detached from the carrier tape.
The present invention provides a cover tape which can prevent the above-mentioned troubles associated with peeling strength or appearing during mounting, which can be produced at a low cost, and which is transparent.
Also, according to the present invention, by reducing the production steps such as dry lamination, extrusion lamination and the like, the amount of an organic solvent used can be decreased, resulting in reduced environmental pollution and, moreover, the energy required can be saved.
The present invention further provides a cover tape which has a peeling strength not too high and not too low and small in difference between the maximum value and the minimum value and which has high transparency.
Specifically, the present invention provides the following cover tapes.
(1) A cover tape for packaging electronic components, which can be heat-sealed to a plastic-made carrier tape having pockets capable of storing electronic components, formed regularly therein and which comprises (A) a biaxially oriented film layer made of a polyester, a polypropylene or a nylon and (B) a thermoplastic resin layer composed of 100 parts by weight of an ethylene copolymer and 10 to 100 parts by weight of a polystyrene, laminated to one side of the layer A.
(2) A cover tape for packaging electronic components according to the above (1), wherein at least one kind of layer selected from the group consisting of a non-oriented polyester layer, a non-oriented nylon layer and a non-oriented polypropylene layer is interposed between the layer A and the layer B.
(3) A cover tape for packaging electronic components according to the above (1) or (2), wherein a comonomer of the ethylene copolymer contained in the layer B is at least one kind selected from the group consisting of vinyl acetate, acrylic acid, an acrylic acid ester, methacrylic acid, a methacrylic acid ester and an ionomer.
(4) A cover tape for packaging electronic components according to the above (1) or (2), wherein the proportion of a comonomer of the ethylene copolymer contained in the layer B is 17 to 90 parts by weight relative to 100 parts by weight of ethylene.
(5) A cover tape for packaging electronic components according to the above (1) or (2), wherein the layer B has a thickness of 0.5 to 50 xcexcm.
(6) A cover tape for packaging electronic components according to the above (1) or (2), wherein the layer B gives rise to cohesive failure and peeling when the cover tape is heat-sealed to the carrier tape and then is peeled from the carrier tape.
(7) A cover tape for packaging electronic components according to the above (1) or (2), wherein an electrically conductive fine powder made of tin oxide, zinc oxide, titanium oxide, carbon black or a combination thereof and/or a surfactant is dispersed in the layer B and the layer B has a surface resistivity of 1xc3x971013 xcexa9/xe2x96xa1 or less.
(8) A cover tape for packaging electronic components according to the above (1) or (2), wherein an antistatic layer which has dispersed therein an electrically conductive fine powder made of tin oxide, zinc oxide, titanium oxide, carbon black or a combination thereof and/or a surfactant, is formed on the surface of the layer B and the antistatic layer has a surface resistivity of 1xc3x971013 xcexa9/xe2x96xa1 or less.
(9) A cover tape for packaging electronic components according to the above (1) or (2), which has a peeling strength of 0.1 to 1.3 N per mm of the sealed width of the tape, when the cover tape is heat-sealed to the carrier tape and then peeled from the carrier tape.
(10) A cover tape for packaging electronic components according to the above (1) or (2), which has a luminous transmittance of 70% or more and a haze of 80% or less.
(11) A cover tape for packaging electronic components according to the above (1) or (2), which has a difference between the maximum value and the minimum value in peeling strength, of 0.01 to 0.4 N per mm of the sealed width of the tape, when the cover tape is heat-sealed to the carrier tape and then peeled from the carrier tape.
(12) A cover tape for packaging electronic components, which can be heat-sealed to a plastic-made carrier tape having pockets capable of storing electronic components, formed regularly therein and which comprises at least two layers of an adhesive layer and a base layer, the adhesive layer being present at the side of the cover tape heat-sealed to the carrier tape, the two layers being laminated with each other by co-extrusion, and the base layer being a polyester, a nylon or a polypropylene.
(13) A cover tape for packaging electronic components, which can be heat-sealed to a plastic-made carrier tape having pockets capable of storing electronic components, formed regularly therein and which comprises at least three layers of an adhesive layer, an interlayer and a base layer in this order, the adhesive layer being present at the side of the cover tape heat-sealed to the carrier tape, the interlayer and the base layer being laminated with each other by co-extrusion, and the adhesive layer being laminated by gravure coating.
(14) A cover tape for packaging electronic components according to the above (12), wherein the adhesive layer is made of an ethylene-xcex1-olefin copolymer and the xcex1-olefin is vinyl acetate, acrylic acid, an acrylic acid ester, methacrylic acid or a methacrylic acid ester.
(15) A cover tape for packaging electronic components according to the above (13), wherein the interlayer is made of an ethylene-xcex1-olefin copolymer and the xcex1-olefin is vinyl acetate, acrylic acid, an acrylic acid ester, methacrylic acid or a methacrylic acid ester.
(16) A cover tape for packaging electronic components according to the above (13) or (15), wherein the adhesive layer is made of an ethylene-xcex1-olefin copolymer wherein the xcex1-olefin is vinyl acetate, acrylic acid, an acrylic acid ester, methacrylic acid or a methacrylic acid ester, a poly(methacrylic acid ester), a vinyl chloride-vinyl acetate copolymer, a polypropylene chloride or a polyurethane.
(17) A cover tape for packaging electronic components according to any of the above (12) to (15), which has a luminous transmittance of 70% or more and a haze of 60% or less.